After a series of terrorist attacks by extremists from both religious communities over recent years, and a history of inter-faith violence, such views are deeply controversial.

Both the opposition Hindu nationalist Bharatiya Janata party (BJP) and the ruling Congress party regularly accuse one another of playing on communal divisions for political aims.

Spokesmen for the BJP said Rahul Gandhi, who leads the youth wing of the ruling Congress party, had been "irresponsible".

"In one stroke, Rahul Gandhi has sought to give a big leverage to the propaganda of all terror groups operating from Pakistan and certain segments of the Pakistan establishment," Ravi Shankar Prasad, a BJP leader, said.

Prasad said the statement showed how little Gandhi, the son of the Italian-born Congress party president, Sonia Gandhi, knows about India.

The Congress spokesman Manish Tiwari said the BJP "should act responsibly on the issues of national importance".

"[The] Bharatiya Janata party has a habit of communalising and politicising everything. Congress has always maintained that terrorism does not have any religion, terrorism does not have any caste and to fight terrorism is the duty of every Indian citizen," he told reporters.

The cable gave details of a presentation by the ICRC in which US diplomats heard of the systematic use of torture involving beatings, stretching and electric shocks in Kashmir between 2002 and 2004, based on research the humanitarian organisation had conducted in the violent former Himalayan princely state.

A spokesman for the ministry of external affairs in Delhi said India "is an open and democratic nation which adheres to the rule of law".

"If and when an aberration occurs, it is promptly and firmly dealt with under existing legal mechanisms in an effective and transparent manner," the spokesman added.

"In India, there is a healthy tradition of democratic debate and freedom of expression on all issues that concern the welfare of our citizens anywhere in our country. Neither have we shied away from an open and candid discussion on such issues when raised by our international friends and partners."

The ICRC declined to comment on the cable.

The controversy over Rahul Gandhi comes at a bad time for the ruling coalition government, which has been hit by a series of corruption scandals that have badly dented its image.

Criticism of other senior Congress figures in the cables, including Sonia Gandhi, led to headlines describing India's first family as "Wiki-bombed" by a "twin Wiki-blast".